Field
Embodiments of the present invention generally relate to plasma cleaning or etching in the process of fabricating integrated circuits. In particular, the invention relates to a process kit for a plasma chamber.
Description of the Related Art
Plasma chambers are used in integrated circuit manufacturing to remove contaminants from the surface of a substrate and/or to etch surfaces of a substrate. To perform a plasma cleaning or etching process, an integrated circuit is placed in a plasma chamber and a pump removes most of the air from the chamber. A gas, such as argon, can then be injected into the chamber. Electromagnetic energy (e.g., radio frequency) is applied to the injected gas to excite the gas into a plasma state. The plasma releases ions that bombard the surface of the substrate to remove contaminants and/or material from the substrate. Atoms or molecules of the contaminants and/or substrate material are etched from the substrate and are, for the most part, pumped out of the chamber. However, some of the contaminant and/or etched material may be deposited on surfaces of the chamber.
Some plasma process chambers are designed with liners having walls that form a tortuous flow path for gasses passing through the chamber. The parts of the plasma process chamber that form the liners are referred to as a process kit. The walls of the liners trap the plasma in the chamber while providing a path for the displaced contaminants and/or substrate materials to escape. Inevitably, some of the displaced materials are deposited on the walls of the chamber, especially at corner locations where the displaced materials change direction. Eventually, the parts making up the process kit need to be cleaned or replaced due to the buildup of displaced materials. Otherwise, the buildup of displaced materials could become a particle source that could affect chip yield.
FIG. 1 is a cross-sectional schematic side view of one embodiment of a conventional plasma processing chamber 100 in which a process kit may be used. The plasma processing chamber 100 includes chamber walls 104 and a lid 102 that define a volume. The lid includes a port 106 through which a process gas, such as argon, can be introduced. The wall 104 includes a port 108 through which contaminants and/or substrate materials removed from a substrate 126 and any plasma that escapes the process region 132 can be removed. For example, the port 108 could be in communication with a pump (e.g., a turbo pump) that pulls such materials out of the volume. The plasma processing chamber 100 includes a pedestal 124 on which a substrate 126 can be mounted for processing. The pedestal 124 and the substrate 126 can be in electrical communication with a radio frequency source 128 (e.g., a dual frequency radio frequency source). The electromagnetic energy transmitted by the radiofrequency source 128 through the pedestal 124 excites the process gas into a plasma 130 above the substrate 126. The plasma processing chamber 100 also includes a process kit that defines boundaries of the process region 132. The process kit includes an upper shield 110 and a lower shield 116.
The upper shield 110 includes a top portion 115 and a cylindrical liner 114. The lower shield 116 includes a horizontal portion 118 extending from the pedestal 124 and a vertical portion 120 extending from the horizontal portion 118. Generally, the lower shield 116 is electrically isolated from the pedestal 124 by an insulating material. The upper shield 110 and the lower shield 116 include and/or define apertures that provide a fluid flow path from the port 106 in the lid to the port 108 in the wall 104. The top portion 115 of the upper shield 110 includes a plurality of apertures 112 arranged around the circumference of the top surface 115 that allow process gas into the process region 132. The cylindrical liner 114 of the upper shield 110 and the vertical portion 120 of the lower shield 116 define an annular aperture or apertures 122 there between that enable materials removed from the substrate 126 to escape. Arrows A-F illustrate the flow of process gas into the plasma process chamber and the flow of contaminants and/or substrate material out of the plasma processing chamber 100. Arrow A illustrates the process gas entering through the port 106 in the lid 102. The process gas may be provided by a supply line, a pressurized canister, or the like that is connected to the port 106. As illustrated by arrow B, after entering through the port 106, the process gas travels radially outward toward the apertures 112 in the upper shield 110. The process gas then passes through the apertures 112 in the direction of arrow C to enter the process region 132. In the process chamber, the process gas is ignited to form a plasma by the electromagnetic energy from the radiofrequency source 128. The electromagnetic energy also generally contains the plasma 130 in a region above the substrate 126. The ions from the plasma bombard the surface of the substrate 126, causing contaminants and/or substrate material to be released from the surface of the substrate 126. The released contaminants and/or substrate material exits the process region 132 through the annular aperture 122 between the cylindrical liner 114 of the upper shield 110 and the vertical portion 120 of the lower shield 116, as indicated by arrow D. The released contaminants and/or substrate material can then move past the lower shield in the direction of arrow E and can then exit the plasma processing chamber 100 through the port 108 in the wall 104, as indicated by arrow F. As discussed above, a pump, such as a turbo pump, can provide a vacuum that urges the contaminants and/or substrate material to exit the plasma processing chamber 100.